基于结构力学的沿空留巷顶板变形控制原理研究与应用

Research and Application of Control Principle on Roof Deformation of Gob-side Entry Retaining Based on Structural Mechanics

为了进一步研究沿空留巷顶板变形控制原理,基于悬臂梁结构力学模型,给出了卸压支护条件下顶板固定端弯矩及自由端扰度计算公式。根据公式可知:固定端弯矩与悬臂梁长度的2次方呈正比,末端挠度与悬臂梁长度的4次方呈正比,通过切顶缩短悬臂梁长度,可以几何级降低悬臂梁弯矩及挠度;加密加强锚索支护,将顶板叠合梁串连形成组合梁,大幅增加了顶板整体性和抗弯能力;悬臂梁自由端加载支撑力,可以线性降低悬臂梁固定端弯矩及自由端挠度,自由端挠度为0时,支撑力需达到2~3倍单位面积地压力。根据公式可总结沿空留巷顶板变形控制三原理及对应的顶板变形控制三要素。采用FLAC7.0软件对6种工况进行了模拟计算,切顶卸压与墙体联合留巷并适当让压取得了最佳效果,切顶、巷旁墙体支撑分别对于降低顶板变形起到40%、50%的作用。进行了切顶卸压与柔模墙联合沿空留巷工业性试验,留巷一次回采断面收缩率19%,留巷二次回采无返修,留巷效果良好。

In order to further study the roof deformation control principle of gob-side entry retaining,based on the cantilever beam structural mechanics model, the calculation formulas of the bending moment of the fixed end and the disturbance of the free end of the roof under the pressure relief support are given. According to the formula, the bending moment of the fixed end is proportional to the quadratic of the cantilever beam length, and the end deflection is proportional to the quartic of the cantilever beam length. By reducing the length of the cantilever beam through the roof cutting, the bending moment and deflection of the cantilever beam can be reduced at the geometric level. Encrypt and strengthen the anchor cable support, the roof composite beam series formed composite beam,greatly increasing the integrity and bending capacity of the roof;the bending moment of the fixed end and the deflection of the free end of the cantilever beam can be linearly reduced by loading the support force at the free end of the cantilever beam. When the deflection of the free end is zero, the support force needs to reach 2-3 times the ground pressure per unit area. According to the formula, the three principles of roof deformation control of gob-side entry retaining and the corresponding three elements of roof deformation control can be summarized. The FLAC7.0 software was used to simulate the six working conditions. The roof cutting and unloading combined with the wall retaining roadway and appropriate pressure to achieve the best results. The roof cutting and the wall support near the roadway play a role of 40% and 50% respectively in reducing roof deformation. The industrial test of gob-side entry retaining combined with roof cutting and pressure relief and flexible formwork wall was carried out. The shrinkage rate of the first stoping section of the entry retaining was 19%, and there was no repair in the second stoping of the entry retaining. The effect of the entry retaining was good.